Flatstep ladder



G. LIEBLEQN FLATSTEP LADDER Oct. 31, 1967 Filed Aug. 25, 1966 FIG. IA,

llo

INVENTOR George Lieb/ein United States Patent Office 3,349,870 Patented Oct. 31, 1967 3,349,870 FLATSTEP LADDER George Lieblein, P0. Box 776, Amityville, N.Y. 11701 Filed Aug. 25, 1966, Ser. No. 575,163 7 Claims. (Cl. 182-228) The present invention relates to metal ladder constructions of the step ladder or extension ladder types; and is more particularly concerned with an improved ladder characterized by a novel rung construction and by a novel assembly arrangement for aflixing such rungs to the side rails of the ladder.

Various forms of metal ladders have been suggested heretofore, comprising, in general, a pair of metallic side rails having a plurality of spaced metallic rung elements extending therebetween and fastened thereto. One Wellknown form of rung used in such constructions is of rounded tubular configuration; and rungs of this type are often fastened to the ladder side rails by forming circular holes in the side rails through which the opposing ends of each tubular rung are caused to extend, with the rung then being fastened in place by rolling the outermost end of each lung over the edges of said holes provided in the ladder side rails. Assembly of this type can be readily effected on commercially available assembly machines; whereby the overall construction lends itself to mass production.

Round rung ladders of the type described above have the disadvantage that a round rung provides a relatively uncomfortable base on which to stand, and also affords a very small surface contact between the rung and the feet of a person standing on the ladder, whereby it is relatively easy to slip on the rungs. In an effort to overcome these known disadvantages, various alternative, more costly, metal rung constructions have been suggested, wherein the rung is characterized by an uppermost relatively flat surface. The use of such flatstep metal rungs has greatly complicated ladder manufacture, and has increased the cost of ladders over and above the increased cost of the rungs themselves. In general, for example, flat-step metal rungs of types suggested heretofore have not been provided with circular ends, wherefore it is not feasible to mount the ends of said rungs in circular apertures provided in the ladder side rails. To the contrary, the special flatstep rung shapes suggested heretofore have required that the ladder side rails be provided with special, and costly, retaining brackets or clamps; or that said side rails be provided with specially-shaped noncir-cular apertures, again at a considerable increase in cost. And even with these special mounting arrangements, the resultant joints between the flatstep rung and its associated side rails are often weaker and less reliable than had been the case with earlier round rung arrangements.

The present invention, recognizing the fabrication, cost, and strength advantages which can be accomplished in round rung ladders, and simultaneously recognizing the advantages of comfort and safety which are achieved in flatstep ladders, provides a novel ladder construction which combines the advantages, while simultaneously eliminating the disadvantages, of both types of ladder. In this respect, as will appear, the present invention provides a ladder utilizing a novel elongated rung having a flat upper portion throughout its major extent whereby the comfort and safety of the ladder in use corresponds to that of flatstep ladders already known in the art; and wherein the ends of the novel rung are formed in rounded sections, with associated beads, so that the rungs can be attached to the ladder side rails with far greater ease and at less expense than is the case with known flatstep ladders, and by the use of conventional assembly machines. In this respect, moreover, the present invention is further characterized by a rung of novel configuration, capable of being fabricated by conventional extrusion techniques followed by relatively simple forming operations, whereby the cost of the rung is far less than would be the case if some highly complex casting or machining techniques were needed.

It is accordingly an object of the present invention to provide a flatstep ladder characterized by novel flatstep rungs adapted to be attached to the ladder side rails in a simple and more reliable manner than has been the case in flatstep ladders suggested heretofore.

Another object of the present invention resides in the provision of an improved metal ladder structure having side rails provided with circular apertures adapted to receive and retain flatstep rungs.

A still further object of the present invention resides in the provision of an improved flatstep ladder which is easier and less expensive to manufacture than flatstep ladders suggested heretofore.

Another object of the present invention resides in the provision of an improved ladder side rail-rung assembly, which avoids the need of special brackets or other facilities for supporting a flatstep rung against rotation in bearing holes provided in the side rails.

Still another object of the present invention resides in the provision of a novel ladder rung characterized by a unique configuration of central and end portions whereby said rung provides the safety and stability advantages of flatstep ladders, in combination with the assembly, cost, and joint strength advantages of round rung ladders.

In providing for the foregoing objects and advantages, the present invention contemplates the provision of a metal ladder comprising a pair of side rails (which may take the form of I beam extrusion) supporting a plurality of spaced flatstep rungs. Each of said rungs is provided with an upper substantially flat surface; and, in a preferred embodiment, the rungs comprise hollow metal extrusions (e.g. aluminum, magnesium, or the like) having a substantially D cross sectional configuration.

Rungs having some form of D cross sectional configuration have, in themselves, been suggested heretofore; but rungs of this general type have normally been attached to the ladder side rails by relatively complex means, e.g., through the use of specially shaped bearing holes, or special brackets or clamps, which greatly increase the cost of assembly and, unfortunately, usually decrease the strength of the joint between the rung and side rails. In accordance with the present invention, the D-shaped rungs are coned at their opposing ends to transform said opposing ends from a D cross section into a circular cross section. The resultant generally cylindrical ends of each rung are then mounted in circular holes, in the ladder side rails, by a relatively inexpensive, but highly reliable, beading and rolling technique. Moreover, as will be described, the rungs and side rails are each ribbed, so that when the ribbed rung ends are inserted into the ribbed ladder side rails, and rolled into place, the ribbing on the rungs and side rails provide a firm lock preventing the rungs from rotating, without the need of any special locking brackets or clamps.

The foregoing objects, advantages, construction and operation of the present invention will become more readily apparent from the following description and accompanying drawings in which:

FIGURE 1A is a perspective view of a portion of a ladder rung extrusion of the type utilized in the present invention;

FIGURE 1B is a perspective view of a portion of a ladder rung construction, of the type shown in FIGURE 1A, formed with a coned end in accordance with the present invention;

FIGURE 1C is a perspective view of the ladder rung portion shown in FIGURE 113, with a bead added thereto; and

FIGURE 2 is a top cross sectional view of one end of a ladder rung constructed in accordance with the present invention, and attached to a ladder side rail.

It will be understood that a ladder constructed in accordance with the present invention comprises a pair of metallic side rails having spaced rungs extending therebetween and attached thereto. One such side rail is illustrated in cross section at in FIGURE 2; and one end of a typical rung 11 is also shown in FIGURE 2. Only one side rail, and only one end of a typical rung, has been shown in FIGURE 2; but it will be appreciated that the other side rail, and the other end of each rung, will also take the form shown in FIGURE 2 (and in the other figures to be described).

In fabricating rungs to be assembled in accordance with the techeniques of the present invention, one first starts with a plurality of D-shaped hollow metallic extrusions of the type shown in part in FIGURE 1A. Each extrusion 1111 has an upper substantially flat surface 11b, and a pair of rounded side surfaces 110 forming a D-shaped hollow cross section as shown at 11d. The top and side surfaces 11b and 11c are, during the formation of the extrusion 11a, formed with a plurality of parallel, elongated, substantially continuous ribs 11c acting to increase the traction between the ultimate rung and the shoes of one standing on that rung. These ribs He also act (as will be described) as a locking means in cooperation with similar ribs 10a, formed on the ladder side rails 10 during the extrusion or other manufacture of said side rails (see FIG- URE 2). The lowermost surface 11f of the rung extrusion 11a can, if desired, also be somewhat flattened as shown in FIGURE 1A; and this lower surface can be ribbed or not as desired.

The extrusion 11a, shown in FIGURE 1, is cut to desired lengths corresponding to the lengths of the rungs desired in the final ladder, and including suflicient excess length to permit the formation of end structures of the types to be described. More particularly, after each rung extrusion 11a is cut to length, its opposing ends are coned to convert said opposing ends into a circular cross section. A typical rung end, so coned, is illustrated in FIGURE 1B. The coning is accomplished by using a forming die which has a conical inner configuration and which is positioned over each end of the D shaped rung extrusion 11a. A conical mandrel is then inserted into the open end of the extrusion (the end 11d shown in FIGURE 1A, for example) and said mandrel is then pressed forward along the axis of the rung to expand the rung ends into a conical shape. The resultant expanded end, at each end of the rung, is designated 11g in the several figures. The ribs 11e, originally provided on the extrusion 11a, appear on the expanded end 11g as well. The D cross section formed by the flat top and curved side portions 11b and 11c of the rung is unchanged throughout most of the rung. Due to the coning operation, however, the ends of the rung now assume a circular; externally ribbed, cross section, designated 12 in FIGURE 1B.

As a next step in the fabrication of my novel rung, a bead 13 is formed on each expanded or coned end 11g of the rung, by means of a heading die, which is itself conventional, and of the known type often used in the fabrication of round rung ladders. The ribs 11e formed on the original extrusion 11a extend over each bead 13 to the outermost ends of the rung, and appear on the portions 14 of the ladder rung between each bead 13 and the adjacent free end of said rung.

The portions 14 at the opposing ends of the ladder rung are of substantially cylindrical configuration, having an exterior ribbed surface as illustrated in FIGURE 10.

These opposing ribbed ends 14 are thus adapted to be inserted through round holes provided in the side rails 10 of the ladder. More particularly, as shown in FIGURE 2, the side rails 10 may comprise an aluminum or other metal extrusion of I-beam cross section, and preferably include a central web 15 having ribs 10a formed on the opposing surfaces thereof. The ribs 10a extend in parallel relation to one another along the direction of extrusion of the side rails 10. The side rails 10 are punched with spaced round holes 16 through which each end 14 of the ladder rung is inserted until the bead 13 bears firmly upon the inner surface of web 15. The ends 14 of the rung are so dimensioned that, when bead 13 bears on the inner surface of web 15, a portion of each end 14 protrudes outwardly past the outer side of web 15; and these outer protruding ends of the rungs are then rolled to produce an external bead 17. Since rung bead 13 is ribbed, and since the rolled edge or head 17 is also ribbed, these ribs (which are, in effect, portions of the ribs 112 formed in the original rung extrusion) lock into engagement with the ribs 10a on web 15 of the ladder side rail 10. As a result, the ladder rung is firmly held against rotation without the need of any special brackets, clamps, or bearing hole shapes.

While I have thus described the preferred embodiment of the present invention, many variations will be suggested to those skilled in the art. The foregoing description is accordingly meant to be illustrative only and is not limitative of my invention; and all such variations and modifications as are in accord with the principles described are meant to fall within the scope of the appended claims.

Having thus described my invention, I claim:

1. In a ladder, a ladder rung comprising an elongated hollow metal extrusion having a flat upper surface portion, a limited portion of said extrusion adjacent each of the opposing ends of said hollow extrusion being smoothly flared into a circular cross section, an upstanding circular bead integrally formed on each of said circular cross section portions at a location spaced from the adjacent free end of said extrusion to provide short substantially cylindrical portions between said beads and the 0pposing free ends of said extrusion respectively adapted for insertion into circular bearing holes in a pair of ladder side rails, and elongated integral ribs formed on said flat upper surface portion and extending substantially uninterrupted across said beads and along said short substantially cylindrical portions for providing a tread surface on said flat surface portion and for simultaneously providing locking means on said beads and on said cylindrical portions adapted to lock said rung against rotation when the opposing ends of said rungs are mounted in said ladder-side rail bearing holes.

2. The structure of claim 1 wherein said hollow metal extrusion has a cross section of substantially D configuration throughout the major portion of its length, the opposing ends of said D shaped extrusion being flared into a substantially conical interior configuration to provide said circular cross sections at said opposing ends.

3. The structure of claim 2 wherein said ribs are formed on both the flat upper surface and on the subjacent curved outer surfaces of said D-shaped extrusion.

4. The structure of claim2 wherein said ladder includes a pair of generally parallel spaced side rails each of which is provided with at least one round bearing hole adapted to receive one of the opposing ends of said rung, said short substantially cylindrical portions adjacent the opposing ends of said rung being of suflicient length to extend completely through said side rails and to protrude beyond the outer surfaces of said rails when said beads are in abutment with the inner surfaces of said rails respectively, the outwardly protruding ends of said short cylindrical portions being rolled across said outer surfaces of rails to hold said rung in place.

5. The structure of claim 4 wherein each of said rails comprises a metal extrusion having a plurality of elongated ribs integrally formed thereon adapted to engage and lock with the ribs on said rung beads.

6. The structure of claim 5 wherein each of said rails includes a further plurality of elongated ribs integrally formed thereon adapted to engage and lock with the ribs on the rolled protruding ends of said rung.

7. The structure of claim 6 wherein each of said rails is of substantially I cross section, said round bearing holes being formed in the web of said I, said pluralities of ribs being formed on the opposing surfaces of said Web respectively.

References Cited UNITED STATES PATENTS 1,045,957 12/1912 Dicks 182-228 2,171,863 9/1939 Pirsoh 182-228 3,168,93 8 2/ 1965 Shaver 182228 3,286,402 11/ 1966 Larson 182-22-8 REINALDO P. MACHA'DO, Primary Examiner. 

1. IN A LADDER, A LADDER RUNG COMPRISING AN ELONGATED HOLLOW METAL EXTRUSION HAVING A FLAT UPPER SURFACE PORTION, A LIMITED PORTION OF SAID EXTRUSION ADJACENT EACH OF THE OPPOSING ENDS OF SAID HOLLOW EXTRUSION BEING SMOOTHLY FLARED INTO A CIRCULAR CROSS SECTION, AN UPSTANDING CIRCULAR BEAD INTEGRALLY FORMED ON EACH OF SAID CIRCULAR CROSS SECTION PORTIONS AT A LOCATION SPACED FROM THE ADJACENT FREE END OF SAID EXTRUSION TO PROVIDE SHORT SUBSTANTIALLY CYLINDRICAL PORTIONS BETWEEN SAID BEADS AND THE OPPOSING FREE ENDS OF SAID EXTRUSION RESPECTIVELY ADAPTED FOR INSERTION INTO CIRCULAR BEARING HOLES IN A PAIR OF LADDER SIDE RAILS, AND ELONGATED INTEGRAL RIBS FORMED ON SAID FLAT UPPER SURFACE PORTION AND EXTENDING SUBSTANTIALLY UNINTERRUPTED ACROSS SAID BEADS AND ALONG SAID SHORT SUBSTANTIALLY CYLINDRICAL PORTIONS FOR PROVIDING A TREAD SURFACE ON SAID FLAT SURFACE PORTION AND FOR SIMULTANEOULSY PROVIDING LOCKING MEANS ON SAID BEADS AND ON SAID CYLINDRICAL PORTIONS ADAPTED TO LOCK SAID RUNGS AGAINST ROTATION WHEN THE OPPOSING ENDS OF SAID RUNGS ARE MOUNTED IN SAID LADDER SIDE RAIL BEARING HOLES. 